1. Field of the Invention
The present invention relates to an apparatus which records information on, or reproduces information from a recording medium, and more particularly, to an actuator of an optical disc system and an apparatus for providing a signal for driving the actuator.
2. Description of the Related Art
Optical disk systems have a light source to record information on an optical disk, which is a recording medium, or reproduce information from the optical disk. The light source requires an actuator for moving a light source over an optical disk.
FIG. 1 is a perspective view of an actuator for an optical disk system. Referring to FIG. 1, the actuator includes a light source and has a width of about 10 mm. The actuator is about 10 mm since a compact disc (CD), a digital versatile disc (DVD), or the like used as an optical disk has a diameter of about 12 cm and a thickness of about 0.1 to 1.2 mm and the light source for recording or reproducing information to or from the optical disk produces light with a wavelength of 405 to 780 nm.
FIG. 2 is a partial cross-section of an actuator for an optical disk system of FIG. 1. Referring to FIG. 2, an operating unit of the actuator includes an objective lens 10 and a liquid crystal (LC) panel 20 and is supported by four suspension wires 40.
The four suspension wires 40 support the operating unit as described above and also deliver a driving signal to a focusing coil 50 and to a tracking coil 60, which drive the operating unit in the focusing direction and the tracking direction, respectively. Also, the actuator of FIG. 2 receives a signal supplied to the LC panel 20 from a driving signal supplying device. The driving signal supplied to the focusing and tracking coils 50 and 60 and the signal supplied to the LC panel 20 are combined before being transmitted through each of the suspension wires 40. The combined signal is separated into the two original signals in the operating unit of the actuator of FIG. 2. The actuator of FIG. 2 requires a demodulator 30 to separate the combined signal.
FIG. 3 is a circuit diagram of the actuator of FIG. 2. Referring to FIG. 3, when the actuator of FIG. 2 receives a current Fcs for driving the focusing coil 50 and a current Trk for driving the tracking coil 60 via the four suspension wires 40, an LC panel driving signal LC1 is added to the current Fcs and an LC panel driving signal LC2 is added to the current Trk. The LC panel driving signals LC1 and LC2 each have a burst frequency of 2 kHz. The demodulator filters off a carrier signal with a frequency of 1 MHz from the received signals to produce square-wave signals 1 and 2, which are used for driving the LC panel 20. Spherical aberration can be corrected using the LC panel 20 by changing the amplitudes of the square-wave signals 1 and 2 or changing the amplitude of a tone-burst wave of the square-wave signals 1 and 2.
The spherical aberration correction can be achieved by using a conventional actuator that includes four suspension wires but requires an extra demodulator chip to which conductive wires coming out of an LC panel are coupled. Also, conductive wires coming out of the demodulator chip must be coupled to the four suspension wires, and the coil driving currents Fcs and Trk and the LC panel driving signals LC1 and LC2 may interfere with one another.
Thus, an optical disk system with a reduced number of suspension wires required for delivering separate driving signals to an actuator without using a demodulator is required.